Last year, the Brazilian town of Piracicaba launched a mosquito apocalypse to combat Zika, dengue fever, and other diseases. One year later, the results show a knockout success, with dengue cases down 91% in one of the city’s test neighborhoods and down 52% across the whole of Piracicaba.

The tool of this mosquito destruction is another mosquito, genetically modified by U.K. company Oxitec. This "friendly" Aedes aegypti insect lives for four days, and its offspring never develop past the larval stage. By seeding the town with 3 to 4 million of these GM mosquitos every month, the modified bugs crowds out the local males, ensuring that the females only produce mutant babies. The GM larvae also glow under special lighting, so they can be counted in the wild. That's how progress is tracked.

In tests, Oxitec’s mosquitos almost eliminated dengue.

In tests, Oxitec’s mosquitos almost eliminated dengue, and the live results show a similarly successful result. In Brazil, there is an official dengue year which is used as a standard for monitoring the disease and things related to it.

USDA

During the last dengue year, in the CECAP/Eldorado neighborhood of Piracicaba, cases of dengue dropped from from 133 to just 12, for a (human) population of 5,000. For all Piracicaba, home to 386,449 people, the number of cases dropped from 3,487 to 1,676. The program has proven so successful that the local government plans to deploy the GM mosquitos across more of the city.

The "Friendly Aedes" is part of a bigger plan to eliminate mosquitos from the city, which also includes eliminating standing water breeding grounds, said the city’s secretary of health Pedro Mello in a press release.

The Friendly Aedes isn’t cheap. To cover the entire city of Piracicaba would cost around $2.7 million a year, but that is almost entirely offset by savings made by not buying spray and larvicides and by not paying sick-leave to dengue sufferers. Part of the ongoing cost is the fact that the Friendly Aedes dies after breeding and has no viable offspring of its own. This means that Oxitec has to keep pumping them into the environment. That’s good for Oxitec’s bottom line, of course, but it also means that, in theory, the Friendly Aedes don’t stick around in the environment.

The success of this live trial, as well as the safety guards built-in to the Friendly Aedes, means that it could be exported to anywhere that has a problem with dengue.

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